Recently, diverse wireless communication technologies are under development in line with the advancement of information communication technology. Among them, a wireless local area network (WLAN) is a technique allowing mobile terminals such as personal digital assistants (PDAs), lap top computers, mobile multimedia players (PMPs), and the like, to wirelessly access the high speed Internet at homes or offices or in a particular service providing area based on a radio frequency technology.
A wireless mesh network may be a network supporting direct communications between a plurality of wireless devices, i.e., mesh points (MPs) having a function of relaying, without going through an access point (AP). From the point of view of the function, a distribution system (DS) connecting the AP may be substituted by an inter-operable wireless links between MPs or multi-hop paths between a plurality of MPs. The mesh network allows one MP to establish a peer-to-peer wireless link with neighboring MPs, having an advantage of enabling more flexible wireless connections.
In the mesh network, one wireless device may be connected to a plurality of wireless devices, establishing a plurality of communication paths. Such communication paths between the wireless devices are called as wireless mesh links or simply mesh links or peer links. The wireless devices are called as the MPs but not limited thereto. Among the MPs, an MP that performs an AP function in addition to its relay function is called as a mesh access point (MAP).
The mesh network has advantages of flexibility in network establishment, reliability according to a detour path, and reduction in power consumption resulting from the reduction in a communication distance. Specifically, using the mesh network enables MPs to establish a flexible network therebetween even in an area with no established communication network. In addition, in the mesh network, a plurality of detour paths can be secured as the plurality of MPs are connected to each other, so even if one MP has a trouble, data can be transmitted via a different path. Also, although a communication coverage of one MP is not large, communication can be made by way of an adjacent MP, allowing performing of long distance communication even at a low power level.
A hybrid wireless mesh protocol (HWMP) is one of path selection protocols used in the mesh network. The HWMP is a protocol obtained by combining flexibility in selecting an on-demand path with a proactive topology tree extension. The proactive element and a reactive element combined in the HWMP allow an optimum and effective path selection in significantly diverse types of mesh networks.
The HWMP uses the same protocol primitive, generation and processing rules as those adopted for an ad hoc on-demand distance vector (AODV) protocol. Such HWMP supports two operation modes based on its configuration: an on-demand mode and a proactive tree building mode. The two operation modes are not exclusive but may be used together.
Meanwhile, the MPs constituting the mesh network may operate in one of the two power management modes, respectively. The two power management modes refer to an active mode (AM), a complete power state, and a power save mode (PSM) in which the transmission or receipt of data frame is not allowed and waiting in the least power state. Aside from an MP operating in the AM, in case an MP operating in the PSM receives a data frame to be relayed, the MP cannot transmit the data frame immediately because of the operation characteristics of the PSM, resulting in a high possibility of inevitably generating a transmission delay of a certain time.